Centrifugal casting machine



1966 cs. D. ANDERSON 3,234,604

CENTRIFUGAL CASTING MACHINE Filed Feb. 18, 1963 2 Sheets-Sheet l INVENTOR H6 2 4RV D ANDERSON ATTORNEY Feb. 15, 1966 G. D. ANDERSON 3,234,604

CENTRIFUGAL CASTING MACHINE Filed Feb. 18, 1963 2 Sheets-Sheet 2 INVENTOR GARY D. ANDERSON BY (Awwfilg ATTORNEY United States Fatent C) 3,234,604 CENTRIFUGAL CASTING MACHINE Gary D. Anderson, South St. Paul, Minn., assignor to Torit Manufacturing Company, St. Paul, Minn., a corporation of Minnesota Filed Feb. 18, 1963, Ser. No. 259,014 4 Claims. (Cl. 22-651) This invention relates to an improvement in centrifugal casting machines and deals particularly with a device used by dentists and dental laboratories in the casting of crowns, inlays, bridges, and the like.

Centrifugal casting machines capable of making small castings of gold and other such metals have long been employed. In general, these devices include a base supporting a horizontal shaft, and a means of rotating the shaft for a predetermined period of time. An arm is supported on an end of the shaft which includes a support for a casting ring and a crucible extending in a generally radial direction from the shaft, and the shaft is counter-balanced to rotate frequently when the mold is in place. After the metal has been heated to a molten state, the shaft is permitted to rotate forcing the molten metal outwardly by centrifugal force to fill the mold cavity. In some instances, suction is applied to the outer end of the casting ring to reduce air pressure in the mold cavity.

The present invention resides in an improved device of the general type described, the device including an improved spring motor and overrunning clutch arrangement and also including a novel means of evacuating air from the mold support which makes the apparatus somewhat simpler to construct and maintain, and which insures the proper operation of the apparatus over a relatively long period of time.

These and other objects and novel features of the present invention will' be more clearly and fully set forth in the following specification and claims.

In the drawings forming a part of the specification;

FIGURE 1 is a perspective view of the apparatus in readiness to receive the mold.

FIGURE 2 is a vertical sectional view through the apparatus showing the general arrangement of parts therein.

FIGURE 3 is a sectional view through a portion of the mold support.

FIGURE 4 is a side elevational view of the device in readiness to receive the mold.

FIGURE 5 is a detail view of a portion of the spring motor and clutch unit.

FIGURE 6 is a sectional view through the drive shaft, the position of the section being indicated by the line 66 of FIGURE 5.

FIGURE 7 is another sectional view through the drive shaft, the position of the section being indicated by the line 77 of FIGURE 5.

The casting apparatus is indicated in general by the letter A, and is shown in its assembled form in FIGURE 1 of the drawings. The device A includes a heavy base portion 10 having a hollow under surface as indicated in dotted outline in FIGURE 4 of the drawings by the numeral 11. The base 10 is provided with a central generally rectangular boss 12 extending upwardly from the upper surface, and a rectangular open frame 13 is anchored to the boss 12 by bolts 14. The open vertical ends of the frame 13 are internally grooved as indicated at 15 to accommodate removable closure plates such as 16. Generally triangular corner portions 17 strengthen the corners of the frame 13 and are provided with internally threaded holes 19 designed to accommodate the fastening bolts 20 for holding the cover plates 16 in place.

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A hollow shaft 21 is supported by the frame on a apertured to accommodate a bearing 23 supporting one end of the shaft 21. The opposite vertical side 24 of the frame 13 is provided with a boss 25 having an aperture 26 extending therethrough in axial alignment with the axis of the bearing '23 and which accommodates a second shaft supporting bearing 27. A bearing sleeve 29 is rotatably supported upon the shaft 21 between the frame sides 22 and 24, and a clutch disk 30 is supported by this sleeve 29. A second clutch disk 31 is supported on the shaft 21 adjoining the clutch disk 30 and is held from rotation relative to the shaft. Ratchet teeth 32 (FIGURE 5) project from the clutch disk 30 and are engageable with cooperable clutch teeth 33 on the clutch disk 31. The shaft 21 is axially slidable in its bearings 23 and 27 to permit engagement and disengagement of the teeth 32, 33.

A torsion spring 34 encircles the sleeve 29 and has an end 35 bent parallel to the spring axis to extend through an aperture 36 in the clutch collar 30. The other end of the spring 34 is anchored to the wall 24 of the frame 13 as indicated at 37 in FIGURE 2 of the drawings.

A mold supporting bracket arm indicated in general by the numeral 39 is provided with a cylindrical hub 40 securely mounted on the end of the hollow shaft 21. The end '41 of the bracket arm 39 which adjoins the hub 40 includes a short generally radially extending arm portion 42- which curves at right angles to form an arm portion 43 which extends parallel to a radius from the axis of the shaft 21. The arm portion 43 curves to form an arm end 44 which is generally parallel to the short arm portion 43. The arm portions 42, 43 and 44 are cored to provide a continuous passage 45 extending from end to end of the arm. As indicated in FIGURE 2 of the drawings, the passage 45 communicates with an axial passage 46 leading to the end of the hollow shaft 21.

As indicated in FIGURE 3 of the drawings, the arm portion 45 terminates in a generally cylindrical boss 46 having an axially threaded passage 47 therethrough which intersects the passage 45. This passage 47 has its axis located to intersect the axis of the shaft '21. A mold holding tray including a circular base plate 49 is circularly offset at 50 to terminate in a washerlike apertured flange 51. A hollow externally threaded stud 52 having a ring-shaped head 53 is threaded into one end of the internally threaded passage 47 to clamp the tray flange 51 against the arm portion 44. The tray includes a peripheral upstanding wall 54 which terminates in a diversely turned rounded flange 55. V

A screen disk 56 overlies the ring-shaped stud head 53 and is held in place by a washer 57 which is welded or otherwise secured in place. A ceramic gasket 59 overlies the base 49 of the tray and is apertured as indicated at 60 to expose the screen 56. The crucible 61 is adapted to be supported upon the ceramic gasket 59.

A set screw 62 closes the outer end of the passage 47, and a similar set screw 63 is threaded into the boss 46 in a radial direction to close the passage completely through the boss 46. As will be noted from an examination of FIGURE 3 of the drawings, the passage '45 communicates with the passage 47 which is open through the sleeve 52 and screen 53 to the interior of the crucible.

The crucible is held in place by means of a clamp 64 which is slidable longitudinally of the intermediate portion 43 of the arm 39. The particular form. of construction of the clamp is not believed of utmost importance to the present invention, but the clamp comprises a bracket having parallel sides 65 provided at the ends thereof near the hub 40 with inwardly directed opposed ears 66 designed to hold the crucible toward the tray 49. As is indicated in FIGURE 4 of the drawings, the clamping bracket 64 includes an angularly turned flange 67 which extends at right angles to the central portion 43 of the arm 39. A rod 69 is secured to the ear 67 by means of clamping nuts 70. The rod 69 extends through a lug 71 projecting at right angles to the center portion 43 of the arm 39 and is provided with a loop-shaped head 72 which is designed to engage against the lug 71 in normal position. A spring 73 encircles the rod 69 between the lug 71 and one of the clamping nuts 70, the spring acting to urge the clamping bracket 64 toward the tray 49.

A rod 74 is fitted into a socket 75 in the head end 41 of the arm 39 and extends in a direction parallel to the central portion 43 of the arm 39. The rod 74 is on the opposite side of the axis pivot shaft from the central arm portion 43 and supports a weight 76 which is threaded on to the outer end of the arm 74. A lock nut 77 holds the weight 76 in an adjustable position. The weight 76 forms a counter weight for the arm and the crucible and is arranged to provide a smooth rotation of the operating shaft.

With reference now to FIGURE 2 of the drawings, a sleeve bearing 79 is threaded or otherwise secured to the wall 24 of the frame 13 to extend with its axis normal to the plane of the wall. The frame side 22 is provided with an axially aligned aperture 80, and a parallel vertically spaced aperture 81. A J-shaped rod 82 has its long arm 83 extending through the bearing 79 and the aligned aperture 80. The arm is bent to include a vertical portion 84 and a short arm 85 parallel to the arm portion 83. A collar 86 on the long arm 83 forms an adjustable stop for limiting movement of the arm 82 in one direction, and a similar collar 87 on the short arm 85 limits the slidable movement of the arm 82 in the opposite direction. In one extreme position, as illustrated, the long arm 83 of the J-shaped arm 82 extends in the path of movement of the arm 39 and acts to hold the arm from rotation.

A cap plate 89 having a central concave portion 90 is marginally sealed to the frame side wall 22 by rivets 91 or other suitable means, the cap plate overlying the end of the shaft 21 supported by the bearing 23. A screw fitting 92 having an axial passage 93 extending therethrough is threaded into an aperture 94 in the frame wall 22 terminating within the concave portion 90 of the face plate 89. The end of the fitting 92 which terminates within the interior of the frame 13 is connected by a flexible tube 95 through an aperture 96 in the bottom wall of the frame 13, through a corresponding opening 97 in the boss 12 to a point within the hollow base, the tube bending for connection with a second screw fitting 99 extending through a side wall of the base 10. The screw fitting 99 is connected by a flexible conduit 100 or other suitable mean-s to a source of partial vacuum.

From the foregoing description, it will be evident that when the conduit 100 is opened, partial vacuum is produced in the conduit 100, fitting 99, conduit 95, fitting 92, and the interior of the concave portion 90 of the face plate. Air is drawn from the center of the hollow shaft 21, the passage 45, passage 47, the screen 53, and from the bottom of the crucible. Obviously, this vacuum is applied when the heated casting ring and crucible are in place.

In operation, the arm 82 is retracted to the right from the position shown in FIGURE 2 out of the path of the arm 39. The arm 39 and shaft 21 are slid to the left as viewed in FIGURE 2 until the teeth 33 of the clutch collar 31 engage the cooperable teeth 32 on the clutch collar 30. The arm 39 is then manually rotated in a direction to Wind the spring. By varying the tension of the spring, the length of time through which the arm is rotated.may be regulated.

When the spring 34 has been wound to the proper tension the locking arm 82 is slid to the left as viewed in FIGURE 2, and the arm is carefully rotated until it engages the stop arm. At this time, the arm is in the approximate position illustrated in FIGURES 1 and 4 of the drawings.

After this preparation, the crucible and heated casting ring are inserted in place and clamped against the tray 49 by the slidable clamp 64. The metal in the crucible is heated to a molten state while the suction conduit is open. Air and fumes are drawn through the somewhat porous composition during the heating period. At this time, the arm 82 is retracted out of the path of the rotatable arm 39, and the arm 39 is rotated swiftly by the power of the spring 34. When the torsion of the spring decreases, the counterbalanced arm acts as a fly wheel to maintain the speed of rotation of the shaft 21. When this occurs the ratchet teeth 32 and 33 act as cams to slide the collars 30 and 31 apart thus sliding the shaft 21 and the arm 39 a corresponding distance. By the time the arm 39 ceases its rotation, the metal in the mold cavity has solidified sufficiently to remain in its molded shape.

In the past when the base of the casting ring has been subjected to partial vacuum, it has been necessary to provide a fitting encircling the rotatable shaft and sealed with respect thereto communicating with the suction passage through the rotatable arm and with the vacuum source. This seal adds to the friction of the shaft and lowers the efficiency of the unit. By having the hollow shaft terminate in the hollow enclosure on the exterior surface of the frame, the seal can be eliminated. This structure results in materially increasing the effectiveness of the operation.

In accordance with the patent statutes, the principles of construction and operation of this improvement in centrifugal casting machine have beendescribed, and while an endeavor has been made to set forth the best embodiment thereof, it should be understood that changes may be made within the scope of the following claims without departing from the spirit o the invention.

I claim:

1. A centrifugal casting apparatus including,

a support,

a shaft slidably and rotatably supported by said support on a substantially horizontal axis,

a counterbalanced mold supporting arm on one end of said shaft,

drive means detachably engaged with said shaft to drive said shaft,

a vacuum port at one end of said arm and adapted to communicate with the interior of a mold,

said arm having a vacuum passage extending from said vacuum port to the arm axis, 7

said shaft having a vacuum passage extending axially therethrough,

said shaft extending through said support,

a fixed vacuum chamber attached to said support overlying the end of said shaft and free of contact therewith, and

a source of partial vacuum connected to said chamber to withdraw air therefrom.

2. A centrifugal casting apparatus including,

a housing including a generally rectangular frame having substantially vertical parallel walls,

a hollow shaft rotatably supported by said parallel walls,

a counterbalanced mold supporting arm attached to one end of said shaft and extending in a plane generally normal to the axis of said shaft,

said arm having a mold supporting platform at one end thereof positioned to support the mold extending in a radial direction,

said arm having a suction passage extending from said platform to the axis of said arm and communicating with said end of said hollow shaft,

a fixed vacuum chamber mounted on said frame overlying the other end of said shaft and free of contact therewith, and

a vacuum conduit within said frame and terminating in communication with said chamber.

3. A centrifugal casting apparatus including,

a housing including a generally rectangular frame and having substantially vertical parallel walls, a hollow shaft rotatably supported by said parallel walls, a counter-balanced mold supporting arm attached to one end of said shaft and extending in a plane generally normal to the axis of the shaft, said arm having a mold supporting platform at one end thereof positioned to support the mold extending in a radial direction, said arm having a suction passage extending from said platform to the axis of said arm and communicating with said end of said hollow shaft, a fixed vacuum chamber mounted on said frame overlying the other end of said shaft, a vacuum conduit Within said frame and terminating in communication with said chamber, one of said walls including an aperture terminating in said chamber, and a fitting extending into said aperture to which said conduit is secured.

4. A centrifugal casting apparatus including a housing,

a hollow shaft rotatably supported by said housing, a

counter-balanced mold supporting arm attached to one end of said shaft and extending in a plane generally normal to the axis of said shaft, said arm having a mold supporting platform at one end thereof positioned to support the mold extending in a radial direction, said arm having a suction passage extending from said platform to the axis of said arm and communicating with said end of said hollow shaft, a fixed vacuum chamber mounted on said housing overlying the other end of said shaft and free of contact therewith, and a vacuum conduit in said housing and terminating in communication with said chamber.

References Cited by the Examiner UNITED STATES PATENTS 1,113,333 10/1914 Hansen 22-651 1,556,291 10/1925 Maes et al 22-65.1 2,104,380 5/1934 Touceda 2265.1 2,202,473 5/1940 Vickers 2265.1 2,235,443 3/1941 Steinbeck et al. 2265.1 3,052,001 9/1962 Brennan 2265 I. SPENCER OVERHOLSER, Primary Examiner.

MARCUS U. LYONS, Examiner. 

4. A CENTRIFUGAL CASTING APPARATUS INCLUDING A HOUSING, A HOLLOW SHAFT ROTATABLY SUPPORTED BY SAID HOUSING, A COUNTER-BALANCED MOLD SUPPORTING ARM ATTACHED TO ONE END OF SAID SHAFT AND EXTENDING IN A PLANE GENERALLY NORMAL TO THE AXIS OF SAID SHAFT, SAID ARM HAVING A MOLD SUPPORTING PLATFORM AT ONE END THEREOF POSITIONED TO SUPPORT THE MOLD EXTENDING IN A RADIAL DIRECTION, SAID ARM HAVING A SUCTION PASSAGE EXTENDING FROM SAID PLATFORM TO THE AXIS OF SAID ARM AND COMMUNICATING WITH SAID END OF SAID HOLLOW SHAFT, A FIXED VACUUM CHAMBER MOUNTED ON SAID HOUSING OVERLYING THE OTHER END OF SAID SHAFT AND FREE OF CONTACT THEREWITH, AND A VACUUM CONDUIT IN SAID HOUSING AND TERMINATING IN COMMUNICATION WITH SAID CHAMBER. 